Millions of years ago the Baja California peninsula was part of what is now the mainland of Mexico. As the continental crust shifted along the San Andreas fault system, Baja California began to separate from the mainland, moving gradually northwestward. In the process a new sea was created--the Sea of Cortez, or Gulf of California.

The official name of the Sea of Cortez is El Golfo de California (the Gulf of California). On some seventeenth century maps it appears as Mer de Californie (Sea of California) or Mer Vermeille (Vermillion Sea). In 1540 the Spanish navigator Francisco de Ulloa, who discovered that "les Californies" (the Californias) was not an island, named this sea la Mar de Cortés (the Sea of Cortez) after Hernán Cortés, his leader and the conqueror of Mexico. Today the Gulf of California is popularly referred to as the Sea of Cortez. We use both names interchangeably in this book.

The Gulf of California (Plate 1) has been aptly characterized by Dr. Boyd W Walker of the University of California as a "caricature of oceanography" because its oceanographic dynamics are dramatically exaggerated. It has deep basins in its central and lower portions and some of the greatest tides in the world in its upper reaches. It contains over a hundred islands and offshore rocks, and strong upwelling of cold, nutrient-rich waters are evident along both its coasts. The annual sea-surface temperatures in its northernmost portions range from below 50°F (10°C) to more than 90°F (32°C). Because the Gulf acts as a large evaporation basin, its average salinity is higher than that of the Pacific off the Baja California coast. Surrounded by arid deserts, it is buttressed from the cool, moist ocean breezes by high Baja California mountains. The semi-isolation of the Gulf protects it from the swells of the Pacific and makes it appear at times like a large, salty lake, although its tranquility is occasionally disturbed by violent local storms known as "chubascos" and devastating tropical hurricanes.

Rocky shores mark the central and lower Baja coast and occur around nearly all Gulf islands. Hundreds of miles of gently sloping sandy beaches interrupted by short stretches of rocky headlands characterize the mainland. Both coastlines have numerous coves, bays, lagoons, and estuaries bordered by mangrove swamps and salt marshes. The lagoons in the upper Gulf exhibit higher salinities at their heads than at their mouths and thus are considered "negative" estuaries.

These estuarine lagoons, often at the mouths of dried-up river beds, are referred to as "esteros." Estuaries in the lower Gulf are fed by freshwater rivers so that their salinities grade from fresh at their heads to brackish at their mouths, and thus are considered "positive."

Before the construction of the Hoover Dam in 1935 the Colorado River delta was a positive estuarine system. Since that time, dams and the agricultural use of water have literally dried up the lower Colorado River which empties into the Gulf. Evaporation has turned the delta into a negative estuarine system, and formerly brackish areas are now hypersaline.

The great diversity of topographic and bathymetric features of the Gulf of California has produced a variety of habitats for fishes and other marine life. The only thorough analysis of the distribution of Gulf of California fishes was done by Walker (1960). Walker recorded 586 species of fishes in the Gulf which he estimated to constitute 85 to 90% of the actual fish fauna. He analyzed the zoogeographic affinities of 526 shallow-water fishes and noted that 73% of the species are Panamic (tropical), 10% northern (temperate), and 17% endemic, that is, found only in the Gulf of California. He noted that two-thirds of the species have principal ranges extending beyond the Gulf to the south, most as far as Panama. Thirty-eight species range commonly both north and south and 50 species range only to the north. About half of the northern-ranging species occur as disjuncts in the upper Gulf; that is, they also appear along the Pacific coast but are absent or rare in the lower Gulf. The remaining 92 species, which had not been collected outside the Gulf, he considered endemic. Although 36 years of additional collecting, observations, and taxonomic refinements have lowered the number of endemic fish species to 86, Walker's zoogeographical analysis of the Gulf's ichthyofauna has been essentially confirmed (Findley et al., 1996, 1997).

Using this pattern of species distribution, Walker proposed four faunal areas, each characterized by a distinctive assemblage of shore fishes:

the upper Gulf, which extends north of a line from Bahia San Francisquito past the southern tip of Isla Tiburón; ... the central Gulf, which includes the short length of shoreline from Bahia Kino to Guaymas on the east side of the Gulf, and the much longer shoreline between Bahia San Francisquito and La Paz; the Cabo San Lucas area, which extends north from the cape to the vicinity of La Paz, and the southeast Gulf, which includes the low, estero-broken shoreline south of Guaymas (Walker, 1960).

Walker characterized the Gulf fish fauna as being "clearly part of the Panamic fauna." Briggs (1974), in his treatise on marine zoogeography, places the Gulf of California (with its boundaries at La Paz and Topolobampo) in the warm temperate California region mainly because of its wide thermal regime. Rosenblatt (1974) and Hubbs (1974) took exception to this view because of the high number of tropical species in the Gulf, and we agree with them. Even in the far northern Gulf most of the rocky-shore species have tropical affinities (Thomson and Lehner, 1976).

In the 36 years following Walker's 1960 paper numerous collections of fishes were made in the Gulf of California. The University of Arizona has assembled more than 1000 collections from this region (see Figure 1), and many specimens, mainly from the central Gulf, were collected and curated at the Guaymas campus of the Instituto Tecnológico y de Estudios Superiores de Monterrey. Other Mexican institutions, such as the Mazatlán Research Station of the Instituto de Ciencias del Mar y Limnologia of the National Autonomous University (UNAM), the Instituto de Biologia of the same university (in Mexico City), and the Centro Interdisciplinario de Ciencias Marinas (of the National Polytechnic Institute) in La Paz, as well as several California institutions, including Scripps Institution of Oceanography and the University of California, Los Angeles, have made extensive collections in the Gulf. These new data essentially support the boundaries of Walker's faunal areas. For rocky-shore fishes we combine Walker's "Cabo San Lucas area and southeast Gulf" into a lower Gulf region. The reeffish faunas of the Cabo San Lucas-La Paz region and the Topolobampo-Mazatlán region may indeed be distinct enough to justify another subdivision, but reef-fish collections along the predominately sandy shore of the southeastern Gulf are presently inadequate to support another faunal area.

Including deep-sea and pelagic fishes, the Sea of Cortez supports a rich fish fauna of about 875 species (Findley et al., 1996) which can be categorized ecologically by its distinctive communities: (1) pelagic (inshore and offshore surface waters), (2) deep-sea (mesopelagic, bathypelagic, and abyssal), (3) offshore shelf (soft bottoms at intermediate depths), (4) sandy shore and estuarine (inshore soft bottoms), and (5) reef (rocky shores and rocky bottoms). In this book we treat only the reef or rocky-shore fishes, a diverse group of species consisting of 44 families and 281 species.

morena pinta
Muraena lentiginosa
Jenyns, 1842

Illustrated Specimen.

Adult, 17 in. (435 mm), by Tor Hansen; see also Plate 2a; maximum size about 2 ft (0.6 m).

Distinguishing Characteristics

Adult moray eels in the genus Muraena are characterized by tubed anterior and posterior nostrils. The jewel moray can be distinguished from other Gulf morays by its striking color pattern of many light spots ringed by dark brown in chainlike rows over a brown background, but occasionally the spots are indistinct or lacking, and the body appears mottled or reticulated or even almost completely yellow or white. The dorsal fin origin is just behind the head, well in advance of the gill opening.

Distribution.

Distributed throughout the central and lower Gulf, this common moray ranges to Peru and Islas Galápagos. It is also present at Islas Revillagigedo and Isla del Coco.

Ecology.

Primarily a nocturnal predator, the jewel moray feeds largely on crustaceans and fishes. During the day this eel remains under cover in rocky crevices and will defend its shelter against intruders. Some members of the genus (M. helena in the Atlantic) have been reported to be venomous. One of the authors (Kerstitch) was bitten on the finger by a small jewel moray. The bite stung like a bee sting and bled profusely, but no other effects were noticed.

Related Species.

Another species of Muraena, which ranges from Rocas Alijos, far west of Bahia Magdalena, into the Gulf (Guaymas) and south to Peru and the Islas Galápagos, is the argus moray, M. argus (Steindachner, 1870). It can be distinguished from M. lentiginosa by the conspicuous white margin of the dorsal and anal fins and by numerous small white spots scattered over three rows of large irregular yellow blotches on a dark brown ground color (adults). A third species, the hourglass moray, M. clepsydra Gilbert, 1898, ranges from the central Gulf to Peru and the Islas Galdpagos. M. clepsydra has a prominent ocellated black spot ringed with white surrounding the gill openings, lacks white margins on its fins, and has hourglass-shaped light spots on a brown background (juveniles). The adults are speckled with many tiny irregular lightcolored spots on the body and fins.